Determine the electrophysiological mechanisms underlying the phenonmenon of adaptation in neurons, using the nervous system of Aplysia californica. Determine the ionic processes associated with the electrophysiological mechanisms. Investigate the role of calcium in the control of adaptation to determine: (a) if adaptation is calcium dependent; (b) if so, the relationship between intracellular calcium, extracellular calcium, and the barbiturate enhancement of adaptation to include the spectrum of barbiturates from convulsant to anesthetic to anticonvulsant barbiturates; correlate, if possible, the degree of adaptation enchancement with the known clinical actions of the drugs in the spectrum. Test the hypothesis that barbiturates enhance adaptation by promoting increases intracellular levels of free calcium. Determine the effects of other anticonvulsants and anesthetics on adaptation, identifying, if possible, their sites of action.